A bull ring in a big Spanish city on a weekend afternoon: not a place for faint hearts, nor for anyone with ethical qualms about what they are here to see. The plaza is packed to the rafters; there are elderly couples and groups of young women, families, a few teenagers. Imagine a cross between a baseball game, a Roman circus, and a sell-out concert by some X Factor idol. All is noise, heat and shouting and garish colours; a wind band plays Spanish bullfight paso dobles.

Nothing about this scene has changed, in essence, since Hemingway, Orson Welles and Ava Gardner pitched up in Pamplona to sit in the front row and chomp on fat cigars. Out on the circle of sand, a vast open-air theatre, still strut the men in their black winged caps, their neat black slippers, their sparkly traje de luces ("suit of lights"), tighter on their taut bodies than seems either plausible or advisable, and their thick capes of DayGlo violet on one side and canary-yellow on the other.

Even the action, when it happens, seems archaic, timeworn, stuck in a groove of tradition. Out of a gate comes a large black bull moving at great speed, a thick-set beast weighing half a ton. The men in the spangly suits move in, taking the bull around the ring, tiring him out. The banderilleros do their grim business, planting coloured spikes in the bull's back, making the blood stream down its sides. But the torero is the star the public wants to see. He wields the red cape, the bull following it this way and that, creating an effect almost of intimacy as 500 kilos of horned fury brushes past his body. In an unguarded moment, the torero is caught off balance and the bull tosses him on its horns like a rag doll. The crowd screams as the torero staggers to his feet. There is dark blood running down his leg, staining the rich embroidery.

In a world that is bent on putting "reality" in inverted commas, there are few spectacles more viscerally immediate than this. There is plenty of brutality and death on our computer screens, but this live gore-fest is powerfully shocking to sensibilities numbed by virtual horror.

Ten years into the 21st century, it seems extraordinary that a phenomenon like this still has a place at the cultural heart of a modern European nation. There is no underestimating the staying power of a spectacle that some would say forms part of the Spanish national DNA. Yet even in this most tradition-addicted society, the tectonic plates of custom are gradually shifting, and public opinion over the corrida de toros is polarised as never before. On one hand, the Spanish anti-bullfight movement, virtually non-existent 20 years ago, has made huge inroads into a society for whom the notion of animal rights was until recently a puzzlingly alien concept. A proposal is currently going through the Catalan parliament which, if and when it is finally approved this summer, will abolish the corrida once and for all in the region. On the other hand, the news value of the corrida has taken a surprising leap in the past decade, thanks mainly to matador José Tomás – front-page news across the world when he was nearly gored to death in Mexico in April, requiring 17 pints of blood after a bull called Navegante ripped a 15cm hole in his thigh. Not for decades has a matador captured the imagination of bullfight fans like this enigmatic and reclusive man, acclaimed as the saviour of bullfighting for the new dose of glamour he has brought to this most controversial and, some say, anachronistic of sports.

For years the bullfight was an aspect of Spanish culture that admitted no debate: it was beyond discussion, immutable and inscrutable, and if the callow expatriate felt there was something not quite right about the corrida, he would be wise to keep his opinions to himself. But a groundswell is forming. In the past few years, I have begun to witness the previously unthinkable in my adopted home country: heated debates around the dinner table at which, remarkably, a majority of the (Spanish) guests say they have serious reservations about a spectacle that mistreats animals for our viewing pleasure. Pop stars and actors are daring to confess the formerly inadmissible – that the corrida de toros bores and/or disgusts them. Actors Fernando Tejero, Rossy de Palma, singers Alaska and Amparanoia, fashion designer David Delfin and Barcelona footballer Carles Puyol have all come out of the antitaurino closet. Flamenco/hip-hop group Ojos de Brujo are well-known "antis" who last month gave a benefit concert in Barcelona in favour of abolition. Though King Juan Carlos is known to be an aficionado, Queen Sofia recently revealed a royal discrepancy: she is against the bullfight. "Making a bull suffer in the plaza for the public's enjoyment while a few people do business? Let them do what they want, but I won't share it."

Over 20 years of life in Spain, I have observed the ups and downs of this peculiar world, its fads and fashions, its comings and goings of newsworthiness. Fifteen years ago, for example, the biggest story was Jesulín de Ubrique, who wowed the adolescent girls like a Spanish Peter Andre and once made history by performing a bullfight for a strictly all-female audience. ("The only balls in the ring have got to be mine and the bull's," he joked.) Jesulín is (or was, until he aged and calmed down) a clown prince whose performances were pure Benny Hill: at one I went to, the arena was strewn with flowers, condoms, teddy bears and pairs of knickers that the torero would occasionally snatch from the sand and hold to his face while the bull stood panting before him.

In 1936, Federico García Lorca described the bullfight as "probably Spain's greatest poetic and life-sustaining wealth... the most cultured fiesta anywhere in the world". The word "fiesta" in this context means something more than party. The world of the bullfight likes to refer to itself grandiloquently as the fiesta nacional – as though in a land of hundreds of thousands of fiestas, this is the one big celebration all Spaniards can share in. Right up until the turn of the 21st century, to be a bullfight objector was to be stigmatised as lily-livered and unpatriotic. Antonio Moreno, co-ordinator of the Colectivo Andaluz Contra el Maltrato Animal (Andalucian Collective Against Animal Abuse), remembers how, not all that long ago, anyone speaking badly of the bullfight in a public bar risked been thrown into the street. Within the ranks of the pros, detractors and their opinions were batted away with a casual scorn tinged with both xenophobia and sexism: Andrés Amorós, doyen of bullfight theoreticians and author of the bulls-as-culture tome Toros y Cultura (1987), dismisses the antitaurinos as "horrified English spinsters".

Nowadays the opposition is not so easily caricatured – mainly because support for the "anti" cause is no longer marginal. Polls suggest that approximately 70% of Spaniards are uninterested in the corrida, if not actively opposed to it. Pressure groups have sprung up by the dozen, ranging from animal welfare associations such as ADDA (Asociación Defensa Derechos Animal) and the CAS (Anti-Bullfighting Committee), to political parties, Facebook pages and proto-anarchist cells. Many of these groups take their inspiration from the animal rights movement in the US and UK, with ecology and veganism part of the ideological mix.

The antitaurino movement is increasingly vociferous, dynamic and committed. Barely a weekend goes by during the bullfight season without a demonstration outside some city bullring, the protesters daubed with blood and wielding banners with the slogan "Tortura, ni Arte ni Cultura". The antis are wised-up technologically and make good use of the internet (compare the creakily archaic bullfight industry, which continues to function more or less as if the world wide web had never been invented). They are more than willing to take long journeys by rented coach across Spain in search of barbaric bull-based fiestas at which to make their presence felt. In Coria, in the western region of Extremadura, the bull runs at the end of June traditionally featured an "entertainment" in which coloured darts were lobbed at the bull. Last year a group of antis was instrumental in bringing about a municipal ban on this practice. Another barbaric bull-based fiesta is the Toro de la Vega in Tordesillas, near Valladolid, which has become a touchstone for the fast-growing Spanish animal rights movement – for obvious reasons. Each September, a fighting bull is taken into the countryside by townsfolk on horseback and stabbed to death with long lances. This bloody and disturbing ritual engenders annual confrontations between antis from across the country and locals who passionately defend the heritage value of the fiesta.

The protest movement is notably stronger in the north and east, where bull culture is much more rarefied. Of all the Spanish "autonomous communities" it is Catalonia that has become the solar plexus of the antitaurino cause. For Catalan nationalists like Iniciativa per Catalunya, the party shepherding the ban through the Catalan Parliament, bullfighting is political: a 'foreign' custom with no place on Catalan soil. It suits them, therefore, to claim that Catalonia has no real tradition of corrida de toros. In fact this is a piece of bad faith. The curses de braus (Catalan for bullfights) in the province of Tarragona are still enormously popular, whatever Barcelona sophisticates might think. Time was when Barcelona itself was one of Spain's major bullfighting centres, with three rings including Las Arenas (now a shopping centre) and the Plaza de Toros Monumental, where the Beatles performed in 1967. Nonetheless, if the Initiativa Legislativa Popular (ILP) becomes law as expected, the antis will have scored the triumph denied them in more recalcitrant parts of the country.

There is a sense in Spain of a society taking sides, manning the barricades of an issue that has polarised Spanish opinion more widely than ever. The imminent ban in Catalonia has been a hot topic in the bars of Spain for at least the past 12 months. And then there is the other crucial factor: the rise to fame of the matador José Tomás Román Martín. When he burst on to the scene in the late 1990s, the then bullfight critic of El País, Joaquin Vidal, described José Tomás in ecstatic terms as the rebirth of a spectacle that had fallen into decadence and dullness. The corrida Vidal witnessed at Las Ventas on a May day in 1997 was nothing less, he wrote, than the "recovery of the eternal bullfight, the happy reencounter with the greatness of the art of bullfighting. José Tomás has arrived, and with him, there is a before and after in the fiesta."

It is hard to overemphasise the galvanising effect of this man and his art, if that is what it is, on the introverted world of the bullfight. The hardcore of serious aficionados, of which there are as few as in, say, the world of opera, have acclaimed him for the classical perfection of his movements with the cape, which recover classic pasos (movements) such as the manoletina and gaonera. His statuesque posture is admired almost as much as his bravery. Elegance, sobriety, serenity are words commonly used to describe his style. One writer describes his control of space and time in the ring, praising his "cadence, harmony, calm, naturalness". What everyone notices, critics and public, is the way he places himself with regard to the bull as it passes – so close that the horns literally graze the fabric of his suit.

This extraordinary daring, combined with a certain austerity and seriousness, have led Tomás to be placed in the direct lineage of two great historical figures of the bullfighting past, Juan Belmonte and Manolete. As the commentator and retired bullfighter Juan Posada has noted, "José Tomás practises a torero based on basic and classical principles. His merit resides in the way he takes advantage of the situation. He lets the bulls arrive. In our day, he is the torero who comes closest to the almost impossible orthodoxy we dream of. We needed a torero like this, a salutary lesson putting an end to the monotony."

Even non-bullfight fans have been moved by his performance. Catalan actor Ramón Fontserè, who might have been thought to fit the role of antitaurino to a T, emerged from one of Tomás's fights in a dazed state, comparing the bullfighter to Nijinsky. "José Tomás looked to me like a reed rocked by the wind in the centre of the plaza. A miracle, right on the line separating glory from tragedy. I'm not a taurino, but what I've just seen has left me deeply impressed."

As for José Tomás the man, his character has elements of both reactionary and rebel, conservative and iconoclast. If his is a revolution, it will not be televised: José Tomás will not allow his corridas to be broadcast and never gives interviews, creating a media vacuum which, as Leonardo Anselmi of anti-bullfight campaigners Plataforma Prou points out, only serves to swell the cloud of myth already surrounding him. He appears to believe that modern media life is rubbish. "We live in a very superficial age, full of lies. Television interviews are the bane of my profession," he says. Modesty bordering on self-effacement is his default mode. On one of the rare occasions he agreed to talk to the press, his main impulse was to downplay the scale of his impact on the scene. "People say I'm revolutionising the bullfight, but I'm not sure. I can only say that I try to do things the way I feel them. In the old-fashioned way, with a certain purity, as they've always been done in this world."

José Tomás has little in common with other toreros – neither with the vulgar and crowd-pleasing Jesulín de Ubrique, nor with well-born fashion-plates like Cayetano Rivera, who models for Armani. He is neither devoutly Catholic nor stridently rightwing – both par for the course in bullfight circles – and steers well clear of the permanently hungry, gaping maw that is the Spanish celebrity circuit. His friends are intellectuals and artists like actor Albert Boadella, guitarist Vicente Amigo, singers Joaquín Sabina and Joan Manuel Serrat. Most bullfighters would rather live in the countryside amid livestock and country society; not him. Away from the ring, José Tomás lives a quiet life with his girlfriend, Isabel, in the tacky tourist town of Estepona – in its distance from convention, a statement of sorts. Paparazzi images on the web show him strolling on the prom, chewing bubblegum.

Few beyond his closest circle know him at all. One who does, the bullfight writer and biographer Carlos Abella, describes him as "serious, respectful, prudent, educated, discreet, shy, but warm up-close, affable… He doesn't want to know anything about fame. He dislikes going to the tributes and he is uncomfortable with the recognition of his success. He accepts it, but he prefers to be alone, fishing, walking his dogs, driving his fast cars…"

Despite the generally hostile climate surrounding his profession, José Tomás has been making friends in unlikely places. German photographer Anya Bartels-Suermondt has just published a book (José Tomás: Serenata de un Amanecer – "José Tomás: a Dawn Serenade") documenting her 14-year study of man and matador, in images as lushly beautiful as they are frequently terrifying. The textures and colours of the bullfight, from the "suits of lights" to the curdling pools of blood on sand, have rarely been depicted with such obvious admiration. Bartels-Suermondt confesses that her own family, not to mention her German peers, do not generally share her love of the bullfight. Yet, after years of close observation, she believes the corrida de toros is a unique form of culture based on the "artistic union of man and animal". "I respect the opinions of those who don't enjoy the spectacle – but the bullfight is part of world culture, and also deserves our respect. Abolition would be a tragic blow to our democratic right of self-expression." As for her famous subject, she believes him to be a profoundly gifted artist. "The first time you watch him you realise that here is something special. He is more than a torero – he has an aura about him, a charisma, and there is an absolute beauty about what he does. He is extraordinary in every sense."

It is one of the enormous paradoxes of this man that he has galvanised the anti-bullfight cause as much as the world of the bullfight itself. In 2002, José Tomás retired from the profession, needing, he said, time to think. In June 2007, he returned to the ring, choosing as the venue for his messianic comeback the Plaza de Toros Monumental in Barcelona.

The matador's choice of city and plaza was highly significant: for years the huge Monumental bullring had been struggling economically, its downmarket bullfights playing to tourists bussed in from the Costa Brava. Catalan bullfight culture was fading away. At a stroke, José Tomás gave both the Monumental and his local fan base a much-needed shot in the arm. The great and the good of Barcelona society rammed the stalls. Touts demanded up to ¤3,000 a ticket. The bullfight critics – whose reports appear in the arts pages of the Spanish papers – were out in force: José Luis Vadillo of El Mundo spoke of "apotheosis, communion with the public", and a plaza that had become an "altar". El Pais – notionally a leftwing paper – decided that the basis of José Tomás's art was "a poetic and mysterious silence, somewhat hermetic, easier to perceive than to understand… a silence that makes you shudder, because it doesn't shirk from the silence surrounding death". The torero duly won three "ears" (the prized trophy of the corrida) and was carried from the ring on the shoulders of the multitude amid wild scenes of jubilation.

But, as it happens, his return fight turned out to be a watershed as much for the antis as for the pros. Leonardo Anselmi, of the Plataforma Prou, prime mover behind the Catalan bill, describes how the antis' legal masterplan was conceived that day. "It was all thanks to José Tomás," he laughs, revealing a nice sense of irony. "When José Tomás reappeared in the Monumental, until that moment our movement had been a protest movement. Demonstrations, banners, the usual thing. At our first demo in Barcelona, there'd been 300 of us. But the reappearance of this man got us pretty angry, because we realised that the bullfight world was taking the mickey out of us. What had been tradition was now just business. And that's when we started to get political."

That day in Barcelona saw the biggest anti-bullfight demonstration of all time: 5,000 people marched from the Ramblas to the Plaza de Toros Monumental, where the bullfight world was busy acclaiming its conquering hero. From here it was but a step to the massive campaign of signatures – a total of 180,000 were collected across Catalonia – which eventually led to a parliamentary bill.

Three years later, the battle lines are more clearly drawn than ever. Both pros and antis will be crossing their fingers this summer. José Tomás's horrific goring in Aguascalientes, Mexico had left a question mark over the rest of his appearances this year. But the torero has recovered from his wounds in record time – nothing short of a miracle, say his more devoted followers – and is said to be planning a spectacular reappearance. The date of this great event? 18 July – around the same time, say the antis, that the abolition bill is set to become law in Catalonia. The venue? The Plaza de Toros Monumental de Barcelona, scene of the matador's 2007 triumph and symbol of opposition to the fiesta nacional. Unless another bull has its way with him, it won't mean the end of the torero's career. But for the corrida de toros, it might just be the end of an era.